Producing metallic silicid.



THOMAS L. WILLSON, OF OTTAWA, ONTARIO, CANADA.

PRODUCING METALLIC SILICID.

Specification of Letters Patent.

Patented March 12, 1907.

Original application filed April, 11, 1904, Serial No. 202,636. Dividedand this application filed November 5,1906. Serial No. 341,991.

To on whom it may concern:

Be it known that I, THOMAS L. WILLSON, a subject of the King of GreatBritain, residing at Ottawa, Province of Ontario, Canada, have inventedcertain new and useful Improvements in Producing Metallic Silicids, ofwhich the following is a specification.

In my application for patent, Serial No. 202,636, filed April 11, 1904,I have described a process of smelting metallic ores or compoundscontaining silica, or to which silica is added, whereby a metallicsilicid may be produced. The invention described therein relates to thetreatment of silicates or sulfids of nickel, iron, or copper to producesilicids of these metals, either singly or alloyed. The presentapplication is a division of that above referred to and relatesspecifically to the treatment of sulfids.

The process is characterized generically by the treatment of a metallicore or compound by the addition of lime, (or its equivalent,) silica,(if not already contained in sufficient quantity in the ore,) andcarbon, and subjecting the mixture to a sufficiently intense heat for asufficient time to bring about the necessary reduction and reactions.Practically the heat of the electric furnace is essential, and where Ispeak of electrosmelting it is to be understood that I refer to smeltingat a temperature materially above ordinary furnace temperature and suchas can be attained practically only in electric furnaces. If the orecontains sulfur, a proportionately greater quantity of lime is required.The resulting product is a silicid of the metal or metals of the ore orcompound. Thus with a nickel ore the product is a nickel silicid, andwith a nickel-iron ore it is a ferronickel silicid. The remainingproducts of the reactions are either volatilized or discharged as slag.

As one illustration of the practice of my invention I will take the caseof nickel sulfid, to which is added lime, silica, and carbon in suitableproportions, the mixture being heated in an electric furnace, therebyreducing the lime and silica, the calcium combining with the sulfur ofthe nickel sulfid and forming calcium sulfid, which floats as a slag,and the silicon uniting mainly with the nickel to form nickel silicid.As another illustration I may mention the application of my process tothe recovery of iron from the worthless form of iron silicate containingsulfur, which is now a waste product in the reduction of nickel-sulfidores. This material contains already a large percentage of silica, sothat it is unnecessary to add silica. I add a suitable proportion oflime and carbon and smelt in the electric furnace, producing calciumsulfid, which floats off, and iron silicid. If the iron silicatecontains nickel, this will ap ear in corresponding proportion in theresu ting silicid.

My invention is valuable in its application to nickel and iron sulfidores, which ores contain usually a small proportion of copper. With suchores I add a suitable proportion of limestone, silica, and carbon. Ifthis mixture were smelted in a blast-furnace, there would result acalcium silicate of iron and 'a nickel-copper matte but by the moreactive reduction obtainable by electric smelting calcium and silicon arefreed, the calcium uniting with the sulfur of the ore and formingcalcium sulfid, which floats off, and the silicon uniting with thenickel and iron, forming a ferro-nickel silicid. Some of the siliconalso combines with the sulfur to form silicon sulfid, which is volatile.

Theoretically the required proportions should be obtainable thus: Enoughlime or limestone should be added calculated to Gas to combine with thetotal sulfur in the ore. Enough silica should be added to form with thecalcium equivalent thus determined CaO(SiO Then enough carbon should beadded to liberate from the calcium silicate the calcium and silicon, theformer uniting with the sulfur and the latter with the iron and nickel.In practice, however, it is found with sulfid ores that a considerablysmaller proportion of lime, silica, and carbon than theoreticallyindicated may be successfully used. For example, in an electric furnaceusing about thirty-five volts and four thousand amperes the process hasbeen successfully practiced with only half the theoretical proportionsof lime, silica, and carbon. This is probably explainable by the actionof the intense heat of the furnace in dissociating sulfur, which isvolatilized and driven off and could doubtless be recovered as aby-product. Probably this effect would be even greater with a largerelectric furnace generating greater heat.

For the guidance of those skilled in the art I will give in detail theresults obtained in operating with a ferro-nickel-sulfid ore of thefollowing properties, namely: iron, fortyfour to forth-eight per cent;nickel, four to seven per cent. copper, one to two per cent;

ITO

sulfur, twenty-six to twenty-eight per cent. insoluble, (diorite,)fourteen to twenty-two per cent. To three hundred pounds of this oresuitably crushed add one hundred and twenty pounds of crushed limestone,ninetyeight pounds of sand, and one hundred and seven pounds ofgranulated coke. Mix these Well together and feed gradually into aWillson electric-arc furnace in the same manner as in the manufacture ofcalcium carbid. Energizing the furnace With tliirty-i'ive tothirty-seven 'v olts and tour thousand amperes, the reduction of thisquantity of material Will require from tWo to three hours it startedcold. The resulting ferro-nickel silicid has analyzed as follows: iron,75.6 per' cent; nickel, 9.4 per cent; silicon, 12. 16 per cent; sulfur.635 per cent; copper, .76 per cent; unascertained impurities, 1.145 percent; total, 1.00.000.

In running continuously since the calcium sul'lid remains in the furnaceWhen the silicid is tapped off the quantity of lime or limestone usedmay be greatly diminished after the first few hours, the proportion ofsand being correspondingly increased, thereby cheapening the process.For the more complete elimination of the sulfur the heat of the electricl'urnace may be increased, or the proportion of silica may be increased,or fluorspar may be added, preferably shortly before tapping off theproduct,introducing it preferably With a blast of air through twyers.Except for its greater cost fluor-spar (eal ciuin flu orid) might beused to wholly or p a rl ly replace the lime or limestone.

It is to be understood that in the practice of my process limestone maybe used in stead of lime or magnesia (in the form of dolomite, forexample) or any other basic com .1.

pound, as an oXid of an alkaline-earth metal, may be substituted theequivalent of lime, lime (or limestone) being preferable in othercompounds of this class because of its cheapness. The compounds referredto are either natural (ores) or artilicial and may contain. otherimpurities than those specifically mentioned.

What I claim is-- 1. Treating a compound containing lll('li(*l sul'lidby adding a basic compound, silica :1 ml carbon, and elctrosmelting toform a bashsul'fid which slags oil, and a nickel silicid.

Treating a compound containing an iron-nickel sulfid by adding silica, ahashcompound and carbon, and electrosinelting, to produce aiferro-nickel silicid.

3. Treating a compound containing sulfur iron and nickel, by addinglime, silica and carbon, and electrosmelting, to produee a ferro-nickelsilicid.

In Witness whereof I have hereunto signed my name in the presence of twosubscribing Witnesses.

THOMAS L. V7] LLSO. I. Witnesses:

DOMINGO A. Usnm, FRED WHITE.

